sinatra/README.rdoc

= Sinatra

Sinatra is a DSL for quickly creating web applications in Ruby with minimal
effort:

  # myapp.rb
  require 'sinatra'
  
  get '/' do
    'Hello world!'
  end

Install the gem and run with:

  gem install sinatra
  ruby -rubygems myapp.rb

View at: http://localhost:4567

== Routes

In Sinatra, a route is an HTTP method paired with an URL matching pattern.
Each route is associated with a block:

  get '/' do
    .. show something ..
  end

  post '/' do
    .. create something ..
  end

  put '/' do
    .. update something ..
  end

  delete '/' do
    .. annihilate something ..
  end
  
  options '/' do
    .. appease something ..
  end

Routes are matched in the order they are defined. The first route that
matches the request is invoked.

Route patterns may include named parameters, accessible via the
<tt>params</tt> hash:

  get '/hello/:name' do
    # matches "GET /hello/foo" and "GET /hello/bar"
    # params[:name] is 'foo' or 'bar'
    "Hello #{params[:name]}!"
  end

You can also access named parameters via block parameters:

  get '/hello/:name' do |n|
    "Hello #{n}!"
  end

Route patterns may also include splat (or wildcard) parameters, accessible
via the <tt>params[:splat]</tt> array.

  get '/say/*/to/*' do
    # matches /say/hello/to/world
    params[:splat] # => ["hello", "world"]
  end

  get '/download/*.*' do
    # matches /download/path/to/file.xml
    params[:splat] # => ["path/to/file", "xml"]
  end

Route matching with Regular Expressions:

  get %r{/hello/([\w]+)} do
    "Hello, #{params[:captures].first}!"
  end

Or with a block parameter:

  get %r{/hello/([\w]+)} do |c|
    "Hello, #{c}!"
  end

=== Conditions

Routes may include a variety of matching conditions, such as the user agent:

  get '/foo', :agent => /Songbird (\d\.\d)[\d\/]*?/ do
    "You're using Songbird version #{params[:agent][0]}"
  end

  get '/foo' do
    # Matches non-songbird browsers
  end

Other available conditions are +host_name+ and +provides+:

  get '/', :host_name => /^admin\./ do
    "Admin Area, Access denied!"
  end

  get '/', :provides => 'html' do
    haml :index
  end
  
  get '/', :provides => ['rss', 'atom', 'xml'] do
    builder :feed
  end

You can easily define your own conditions:

  set(:probability) { |value| condition { rand <= value } }
  
  get '/win_a_car', :probability => 0.1 do
    "You won!"
  end
  
  get '/win_a_car' do
    "Sorry, you lost."
  end

=== Return values

The return value of a route block determines at least the response body passed
on to the HTTP client, or at least the next middleware in the Rack stack.
Most commonly this is a string, as in the above examples. But other values are
also accepted.

You can return any object that would either be a valid Rack response, Rack
body object or HTTP status code:

* An Array with three elements: <tt>[status (Fixnum), headers (Hash), response body (responds to #each)]</tt>
* An Array with two elements: <tt>[status (Fixnum), response body (responds to #each)]</tt>
* An object that responds to <tt>#each</tt> and passes nothing but strings to the given block
* A Fixnum representing the status code

That way we can for instance easily implement a streaming example:

    class Stream
      def each
        100.times { |i| yield "#{i}\n" }
      end
    end

    get('/') { Stream.new }

== Static Files

Static files are served from the <tt>./public</tt> directory. You can specify
a different location by setting the <tt>:public</tt> option:

  set :public, File.dirname(__FILE__) + '/static'

Note that the public directory name is not included in the URL. A file
<tt>./public/css/style.css</tt> is made available as
<tt>http://example.com/css/style.css</tt>.

== Views / Templates

Templates are assumed to be located directly under the <tt>./views</tt>
directory. To use a different views directory:

  set :views, File.dirname(__FILE__) + '/templates'

One important thing to remember is that you always have to reference
templates with symbols, even if they're in a subdirectory (in this
case use <tt>:'subdir/template'</tt>). You must use a symbol because 
otherwise rendering methods will render any strings passed to them 
directly.

=== Haml Templates

The <tt>haml</tt> gem/library is required to render HAML templates:

  # You'll need to require haml in your app
  require 'haml'

  get '/' do
    haml :index
  end

Renders <tt>./views/index.haml</tt>.

{Haml's options}[http://haml-lang.com/docs/yardoc/file.HAML_REFERENCE.html#options]
can be set globally through Sinatra's configurations,
see {Options and Configurations}[http://www.sinatrarb.com/configuration.html],
and overridden on an individual basis.

  set :haml, :format => :html5 # default Haml format is :xhtml

  get '/' do
    haml :index, :format => :html4 # overridden
  end


=== Erb Templates

  # You'll need to require erb in your app
  require 'erb'

  get '/' do
    erb :index
  end

Renders <tt>./views/index.erb</tt>.

=== Erubis Templates

The <tt>erubis</tt> gem/library is required to render Erubis templates:

  # You'll need to require erubis in your app
  require 'erubis'

  get '/' do
    erubis :index
  end

Renders <tt>./views/index.erubis</tt>.

It is also possible to replace Erb with Erubis:

  require 'erubis'
  Tilt.register :erb, Tilt[:erubis]
  
  get '/' do
    erb :index
  end

Renders <tt>./views/index.erb</tt> with Erubis.

=== Builder Templates

The <tt>builder</tt> gem/library is required to render builder templates:

  # You'll need to require builder in your app
  require 'builder'

  get '/' do
    builder :index
  end

Renders <tt>./views/index.builder</tt>.

=== Nokogiri Templates

The <tt>nokogiri</tt> gem/library is required to render nokogiri templates:

  # You'll need to require nokogiri in your app
  require 'nokogiri'

  get '/' do
    nokogiri :index
  end

Renders <tt>./views/index.nokogiri</tt>.

=== Sass Templates

The <tt>haml</tt> or <tt>sass</tt> gem/library is required to render Sass templates:

  # You'll need to require haml or sass in your app
  require 'sass'

  get '/stylesheet.css' do
    sass :stylesheet
  end

Renders <tt>./views/stylesheet.sass</tt>.

{Sass' options}[http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#options]
can be set globally through Sinatra's configurations,
see {Options and Configurations}[http://www.sinatrarb.com/configuration.html],
and overridden on an individual basis.

  set :sass, :style => :compact # default Sass style is :nested

  get '/stylesheet.css' do
    sass :stylesheet, :style => :expanded # overridden
  end

=== Scss Templates

The <tt>haml</tt> or <tt>sass</tt> gem/library is required to render Scss templates:

  # You'll need to require haml or sass in your app
  require 'sass'

  get '/stylesheet.css' do
    scss :stylesheet
  end

Renders <tt>./views/stylesheet.scss</tt>.

{Scss' options}[http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#options]
can be set globally through Sinatra's configurations,
see {Options and Configurations}[http://www.sinatrarb.com/configuration.html],
and overridden on an individual basis.

  set :scss, :style => :compact # default Scss style is :nested

  get '/stylesheet.css' do
    scss :stylesheet, :style => :expanded # overridden
  end

=== Less Templates

The <tt>less</tt> gem/library is required to render Less templates:

  # You'll need to require less in your app
  require 'less'

  get '/stylesheet.css' do
    less :stylesheet
  end

Renders <tt>./views/stylesheet.less</tt>.

=== Liquid Templates

The <tt>liquid</tt> gem/library is required to render Liquid templates:

  # You'll need to require liquid in your app
  require 'liquid'

  get '/' do
    liquid :index
  end

Renders <tt>./views/index.liquid</tt>.

Since you cannot call Ruby methods (except for +yield+) from a Liquid
template, you almost always want to pass locals to it:

  liquid :index, :locals => { :key => 'value' }

=== Markdown Templates

The <tt>rdiscount</tt> gem/library is required to render Markdown templates:

  # You'll need to require rdiscount in your app
  require "rdiscount"
  
  get '/' do
    markdown :index
  end

Renders <tt>./views/index.markdown</tt> (+md+ and +mkd+ are also valid file
extensions).

It is not possible to call methods from markdown, nor to pass locals to it.
You therefore will usually use it in combination with another rendering
engine:

  erb :overview, :locals => { :text => markdown(:introduction) }

Note that you may also call the +markdown+ method from within other templates:

  %h1 Hello From Haml!
  %p= markdown(:greetings)

Since you cannot call Ruby from Markdown, you cannot use layouts written in
Markdown. However, it is possible to use another rendering engine for the
template than for the layout by passing the `:layout_engine` option:

  get '/' do
    markdown :index, :layout_engine => :erb
  end

This will render <tt>./views/index.md</tt> with <tt>./views/layout.erb</tt> as
layout.

Remember that you can set such rendering options globally:

  set :markdown, :layout_engine => :haml, :layout => :post

  get '/' do
    markdown :index
  end

This will render <tt>./views/index.md</tt> (and any other Markdown template)
with <tt>./views/post.haml</tt> as layout.

It is also possible to parse Markdown with BlueCloth rather than RDiscount:

  require 'bluecloth'
  
  Tilt.register 'markdown', BlueClothTemplate
  Tilt.register 'mkd',      BlueClothTemplate
  Tilt.register 'md',       BlueClothTemplate
  
  get '/' do
    markdown :index
  end

Renders <tt>./views/index.md</tt> with BlueCloth.

=== Textile Templates

The <tt>RedCloth</tt> gem/library is required to render Textile templates:

  # You'll need to require redcloth in your app
  require "redcloth"

  get '/' do
    textile :index
  end

Renders <tt>./views/index.textile</tt>.

It is not possible to call methods from textile, nor to pass locals to it. You
therefore will usually use it in combination with another rendering engine:

  erb :overview, :locals => { :text => textile(:introduction) }

Note that you may also call the +textile+ method from within other templates:

  %h1 Hello From Haml!
  %p= textile(:greetings)

Since you cannot call Ruby from Textile, you cannot use layouts written in
Textile. However, it is possible to use another rendering engine for the
template than for the layout by passing the `:layout_engine` option:

  get '/' do
    textile :index, :layout_engine => :erb
  end

This will render <tt>./views/index.textile</tt> with
<tt>./views/layout.erb</tt> as layout.

Remember that you can set such rendering options globally:

  set :textile, :layout_engine => :haml, :layout => :post

  get '/' do
    textile :index
  end

This will render <tt>./views/index.textile</tt> (and any other Textile
template) with <tt>./views/post.haml</tt> as layout.

=== RDoc Templates

The <tt>rdoc</tt> gem/library is required to render RDoc templates:

  # You'll need to require rdoc in your app
  require "rdoc"

  get '/' do
    rdoc :index
  end

Renders <tt>./views/index.rdoc</tt>.

It is not possible to call methods from rdoc, nor to pass locals to it. You
therefore will usually use it in combination with another rendering engine:

  erb :overview, :locals => { :text => rdoc(:introduction) }

Note that you may also call the +rdoc+ method from within other templates:

  %h1 Hello From Haml!
  %p= rdoc(:greetings)

Since you cannot call Ruby from RDoc, you cannot use layouts written in
RDoc. However, it is possible to use another rendering engine for the
template than for the layout by passing the `:layout_engine` option:

  get '/' do
    rdoc :index, :layout_engine => :erb
  end

This will render <tt>./views/index.rdoc</tt> with <tt>./views/layout.erb</tt> as
layout.

Remember that you can set such rendering options globally:

  set :rdoc, :layout_engine => :haml, :layout => :post

  get '/' do
    rdoc :index
  end

This will render <tt>./views/index.rdoc</tt> (and any other RDoc template)
with <tt>./views/post.haml</tt> as layout.

=== Radius Templates

The <tt>radius</tt> gem/library is required to render Radius templates:

  # You'll need to require radius in your app
  require 'radius'

  get '/' do
    radius :index
  end

Renders <tt>./views/index.radius</tt>.

Since you cannot call Ruby methods (except for +yield+) from a Radius
template, you almost always want to pass locals to it:

  radius :index, :locals => { :key => 'value' }

=== Markaby Templates

The <tt>markaby</tt> gem/library is required to render Markaby templates:

  # You'll need to require markaby in your app
  require 'markaby'

  get '/' do
    markaby :index
  end

Renders <tt>./views/index.mab</tt>.

You may also use inline Markaby:

  get '/' do
    markaby { h1 "Welcome!" }
  end

=== Slim Templates

The <tt>slim</tt> gem/library is required to render Slim templates:

  # You'll need to require slim in your app
  require 'slim'

  get '/' do
    slim :index
  end

Renders <tt>./views/index.slim</tt>.

=== CoffeeScript Templates

The <tt>coffee-script</tt> gem/library and at least <b>one</b> of the
following options to execute JavaScript:

* +node+ (from Node.js) in your path
* you must be running on OSX
* +therubyracer+ gem/library

See http://github.com/josh/ruby-coffee-script for an updated list of options.

Now you can render CoffeeScript templates:

  # You'll need to require coffee-script in your app
  require 'coffee-script'

  get '/application.js' do
    coffee :application
  end

Renders <tt>./views/application.coffee</tt>.

=== Embedded Templates

  get '/' do
    haml '%div.title Hello World'
  end

Renders the embedded template string.

=== Accessing Variables in Templates

Templates are evaluated within the same context as route handlers. Instance
variables set in route handlers are direcly accessible by templates:

  get '/:id' do
    @foo = Foo.find(params[:id])
    haml '%h1= @foo.name'
  end

Or, specify an explicit Hash of local variables:

  get '/:id' do
    foo = Foo.find(params[:id])
    haml '%h1= foo.name', :locals => { :foo => foo }
  end

This is typically used when rendering templates as partials from within
other templates.

=== Inline Templates

Templates may be defined at the end of the source file:

  require 'sinatra'

  get '/' do
    haml :index
  end

  __END__

  @@ layout
  %html
    = yield

  @@ index
  %div.title Hello world!!!!!

NOTE: Inline templates defined in the source file that requires sinatra are
automatically loaded. Call <tt>enable :inline_templates</tt> explicitly if you
have inline templates in other source files.

=== Named Templates

Templates may also be defined using the top-level <tt>template</tt> method:

  template :layout do
    "%html\n  =yield\n"
  end

  template :index do
    '%div.title Hello World!'
  end

  get '/' do
    haml :index
  end

If a template named "layout" exists, it will be used each time a template
is rendered. You can individually disable layouts by passing <tt>:layout => false</tt>
or disable them by default via <tt>set :haml, :layout => false</tt>.

  get '/' do
    haml :index, :layout => !request.xhr?
  end

=== Associating File Extensions

To associate a file extension with a template engine, use
<tt>Tilt.register</tt>. For instance, if you like to use the file extension
+tt+ for Textile templates, you can do the following:

  Tilt.register :tt, Tilt[:textile]

=== Adding You Own Template Engine

First, register your engine with Tilt, then create a rendering method:

  Tilt.register :myat, MyAwesomeTemplateEngine

  helpers do
    def myat(*args) render(:myat, *args) end
  end

  get '/' do
    myat :index
  end

Renders <tt>./views/index.myat</tt>. See https://github.com/rtomayko/tilt to
learn more about Tilt.

== Helpers

Use the top-level <tt>helpers</tt> method to define helper methods for use in
route handlers and templates:

  helpers do
    def bar(name)
      "#{name}bar"
    end
  end

  get '/:name' do
    bar(params[:name])
  end

== Filters

Before filters are evaluated before each request within the same context as
the routes will be and can modify the request and response. Instance variables
set in filters are accessible by routes and templates:

  before do
    @note = 'Hi!'
    request.path_info = '/foo/bar/baz'
  end

  get '/foo/*' do
    @note #=> 'Hi!'
    params[:splat] #=> 'bar/baz'
  end

After filter are evaluated after each request within the same context and can
also modify the request and response. Instance variables set in before filters
and routes are accessible by after filters:

  after do
    puts response.status
  end

Filters optionally taking a pattern, causing them to be evaluated only if the
request path matches that pattern:

  before '/protected/*' do
    authenticate!
  end

  after '/create/:slug' do |slug|
    session[:last_slug] = slug
  end

Like routes, filters also take conditions:

  before :agent => /Songbird/ do
    # ...
  end
  
  after '/blog/*', :host_name => 'example.com' do
    # ...
  end

== Halting

To immediately stop a request within a filter or route use:

  halt

You can also specify the status when halting:

  halt 410

Or the body:

  halt 'this will be the body'

Or both:

  halt 401, 'go away!'

With headers:

  halt 402, {'Content-Type' => 'text/plain'}, 'revenge'

== Passing

A route can punt processing to the next matching route using <tt>pass</tt>:

  get '/guess/:who' do
    pass unless params[:who] == 'Frank'
    'You got me!'
  end

  get '/guess/*' do
    'You missed!'
  end

The route block is immediately exited and control continues with the next
matching route. If no matching route is found, a 404 is returned.

== Accessing the Request Object

The incoming request object can be accessed from request level (filter, routes, error handlers) through the `request` method:

  # app running on http://example.com/example
  get '/foo' do
    request.body              # request body sent by the client (see below)
    request.scheme            # "http"
    request.script_name       # "/example"
    request.path_info         # "/foo"
    request.port              # 80
    request.request_method    # "GET"
    request.query_string      # ""
    request.content_length    # length of request.body
    request.media_type        # media type of request.body
    request.host              # "example.com"
    request.get?              # true (similar methods for other verbs)
    request.form_data?        # false
    request["SOME_HEADER"]    # value of SOME_HEADER header
    request.referer           # the referer of the client or '/'
    request.user_agent        # user agent (used by :agent condition)
    request.cookies           # hash of browser cookies
    request.xhr?              # is this an ajax request?
    request.url               # "http://example.com/example/foo"
    request.path              # "/example/foo"
    request.ip                # client IP address
    request.secure?           # false
    request.env               # raw env hash handed in by Rack
  end

Some options, like <tt>script_name</tt> or <tt>path_info</tt> can also be
written:

  before { request.path_info = "/" }
  
  get "/" do
    "all requests end up here"
  end

The <tt>request.body</tt> is an IO or StringIO object:

  post "/api" do
    request.body.rewind  # in case someone already read it
    data = JSON.parse request.body.read
    "Hello #{data['name']}!"
  end

== Configuration

Run once, at startup, in any environment:

  configure do
    ...
  end

Run only when the environment (RACK_ENV environment variable) is set to
<tt>:production</tt>:

  configure :production do
    ...
  end

Run when the environment is set to either <tt>:production</tt> or
<tt>:test</tt>:

  configure :production, :test do
    ...
  end

== Error Handling

Error handlers run within the same context as routes and before filters, which
means you get all the goodies it has to offer, like <tt>haml</tt>,
<tt>erb</tt>, <tt>halt</tt>, etc.

=== Not Found

When a <tt>Sinatra::NotFound</tt> exception is raised, or the response's status
code is 404, the <tt>not_found</tt> handler is invoked:

  not_found do
    'This is nowhere to be found.'
  end

=== Error

The +error+ handler is invoked any time an exception is raised from a route
block or a filter. The exception object can be obtained from the
<tt>sinatra.error</tt> Rack variable:

  error do
    'Sorry there was a nasty error - ' + env['sinatra.error'].name
  end

Custom errors:

  error MyCustomError do
    'So what happened was...' + request.env['sinatra.error'].message
  end

Then, if this happens:

  get '/' do
    raise MyCustomError, 'something bad'
  end

You get this:

  So what happened was... something bad

Alternatively, you can install error handler for a status code:

  error 403 do
    'Access forbidden'
  end

  get '/secret' do
    403
  end

Or a range:

  error 400..510 do
    'Boom'
  end

Sinatra installs special <tt>not_found</tt> and <tt>error</tt> handlers when
running under the development environment.

== Mime Types

When using <tt>send_file</tt> or static files you may have mime types Sinatra
doesn't understand. Use +mime_type+ to register them by file extension:

  mime_type :foo, 'text/foo'

You can also use it with the +content_type+ helper:

  content_type :foo

== Rack Middleware

Sinatra rides on Rack[http://rack.rubyforge.org/], a minimal standard
interface for Ruby web frameworks. One of Rack's most interesting capabilities
for application developers is support for "middleware" -- components that sit
between the server and your application monitoring and/or manipulating the
HTTP request/response to provide various types of common functionality.

Sinatra makes building Rack middleware pipelines a cinch via a top-level
+use+ method:

  require 'sinatra'
  require 'my_custom_middleware'

  use Rack::Lint
  use MyCustomMiddleware

  get '/hello' do
    'Hello World'
  end

The semantics of +use+ are identical to those defined for the
Rack::Builder[http://rack.rubyforge.org/doc/classes/Rack/Builder.html] DSL
(most frequently used from rackup files). For example, the +use+ method
accepts multiple/variable args as well as blocks:

  use Rack::Auth::Basic do |username, password|
    username == 'admin' && password == 'secret'
  end

Rack is distributed with a variety of standard middleware for logging,
debugging, URL routing, authentication, and session handling. Sinatra uses
many of of these components automatically based on configuration so you
typically don't have to +use+ them explicitly.

== Testing

Sinatra tests can be written using any Rack-based testing library
or framework. {Rack::Test}[http://gitrdoc.com/brynary/rack-test] is
recommended:

  require 'my_sinatra_app'
  require 'test/unit'
  require 'rack/test'

  class MyAppTest < Test::Unit::TestCase
    include Rack::Test::Methods

    def app
      Sinatra::Application
    end

    def test_my_default
      get '/'
      assert_equal 'Hello World!', last_response.body
    end

    def test_with_params
      get '/meet', :name => 'Frank'
      assert_equal 'Hello Frank!', last_response.body
    end

    def test_with_rack_env
      get '/', {}, 'HTTP_USER_AGENT' => 'Songbird'
      assert_equal "You're using Songbird!", last_response.body
    end
  end

NOTE: The built-in Sinatra::Test module and Sinatra::TestHarness class
are deprecated as of the 0.9.2 release.

== Sinatra::Base - Middleware, Libraries, and Modular Apps

Defining your app at the top-level works well for micro-apps but has
considerable drawbacks when building reusable components such as Rack
middleware, Rails metal, simple libraries with a server component, or
even Sinatra extensions. The top-level DSL pollutes the Object namespace
and assumes a micro-app style configuration (e.g., a single application
file, ./public and ./views directories, logging, exception detail page,
etc.). That's where Sinatra::Base comes into play:

  require 'sinatra/base'

  class MyApp < Sinatra::Base
    set :sessions, true
    set :foo, 'bar'

    get '/' do
      'Hello world!'
    end
  end

The methods available to Sinatra::Base subclasses are exactly as those
available via the top-level DSL. Most top-level apps can be converted to
Sinatra::Base components with two modifications:

* Your file should require +sinatra/base+  instead of +sinatra+;
  otherwise, all of Sinatra's DSL methods are imported into the main
  namespace.
* Put your app's routes, error handlers, filters, and options in a subclass
  of Sinatra::Base.

<tt>Sinatra::Base</tt> is a blank slate. Most options are disabled by default,
including the built-in server. See {Options and Configuration}[http://sinatra.github.com/configuration.html]
for details on available options and their behavior.

=== Serving a Modular Application

There are two common options for starting a modular app, activly starting with
<tt>run!</tt>:

  # my_app.rb
  require 'sinatra/base'
  
  class MyApp < Sinatra::Base
    # ... app code here ...
    
    # start the server if ruby file executed directly
    run! if app_file == $0
  end

Start with:

  ruby my_app.rb

Or with a <tt>config.ru</tt>, which allows using any Rack handler:

  # config.ru
  require 'my_app'
  run MyApp

Run:

  rackup -p 4567

=== Using a Classic Style Application with a config.ru

Write your app file:

  # app.rb
  require 'sinatra'
  
  get '/' do
    'Hello world!'
  end

And a corresponding <tt>config.ru</tt>:

  require 'app'
  run Sinatra::Application

=== When to use a config.ru?

Good signs you probably want to use a <tt>config.ru</tt>:

* You want to deploy with a different Rack handler (Passenger, Unicorn,
  Heroku, ...).
* You want to use more than one subclass of <tt>Sinatra::Base</tt>.
* You want to use Sinatra only for middleware, but not as endpoint.

<b>There is no need to switch to a <tt>config.ru</tt> only because you
switched to modular style, and you don't have to use modular style for running
with a <tt>config.ru</tt>.</b>

=== Using Sinatra as Middleware

Not only is Sinatra able to use other Rack middleware, any Sinatra application
can in turn be added in front of any Rack endpoint as middleware itself. This
endpoint could be another Sinatra application, or any other Rack-based
application (Rails/Ramaze/Camping/...).

  require 'sinatra/base'
  
  class LoginScreen < Sinatra::Base
    enable :sessions
    
    get('/login') { haml :login }
    
    post('/login') do
      if params[:name] = 'admin' and params[:password] = 'admin'
        session['user_name'] = params[:name]
      else
        redirect '/login'
      end
    end
  end
  
  class MyApp < Sinatra::Base
    # middleware will run before filters
    use LoginScreen
    
    before do
      unless session['user_name']
        halt "Access denied, please <a href='/login'>login</a>."
      end
    end
    
    get('/') { "Hello #{session['user_name']}." }
  end

== Scopes and Binding

The scope you are currently in determines what methods and variables are
available.

=== Application/Class Scope

Every Sinatra application corresponds to a subclass of Sinatra::Base. If you
are using the top level DSL (<tt>require 'sinatra'</tt>), then this class is
Sinatra::Application, otherwise it is the subclass you created explicitly. At
class level you have methods like `get` or `before`, but you cannot access the
`request` object or the `session`, as there only is a single application class
for all requests.

Options created via `set` are methods at class level:

    class MyApp < Sinatra::Base
      # Hey, I'm in the application scope!
      set :foo, 42
      foo # => 42
      
      get '/foo' do
        # Hey, I'm no longer in the application scope!
      end
    end

You have the application scope binding inside:

* Your application class body
* Methods defined by extensions
* The block passed to `helpers`
* Procs/blocks used as value for `set`

You can reach the scope object (the class) like this:

* Via the object passed to configure blocks (<tt>configure { |c| ... }</tt>)
* `settings` from within request scope

=== Request/Instance Scope

For every incoming request, a new instance of your application class is
created and all handler blocks run in that scope. From within this scope you
can access the `request` and `session` object or call rendering methods like
`erb` or `haml`. You can access the application scope from within the request
scope via the `settings` helper:

  class MyApp < Sinatra::Base
    # Hey, I'm in the application scope!
    get '/define_route/:name' do
      # Request scope for '/define_route/:name'
      @value = 42
      
      settings.get("/#{params[:name]}") do
        # Request scope for "/#{params[:name]}"
        @value # => nil (not the same request)
      end
      
      "Route defined!"
    end
  end

You have the request scope binding inside:

* get/head/post/put/delete/options blocks
* before/after filters
* helper methods
* templates/views

=== Delegation Scope

The delegation scope just forwards methods to the class scope. However, it
does not behave 100% like the class scope, as you do not have the class'
binding: Only methods explicitly marked for delegation are available and you
do not share variables/state with the class scope (read: you have a different
`self`). You can explicitly add method delegations by calling
<tt>Sinatra::Delegator.delegate :method_name</tt>.

You have the delegate scope binding inside:

* The top level binding, if you did <tt>require "sinatra"</tt>
* An object extended with the `Sinatra::Delegator` mixin

Have a look at the code for yourself: here's the
{Sinatra::Delegator mixin}[http://github.com/sinatra/sinatra/blob/ceac46f0bc129a6e994a06100aa854f606fe5992/lib/sinatra/base.rb#L1128]
being {included into the main namespace}[http://github.com/sinatra/sinatra/blob/ceac46f0bc129a6e994a06100aa854f606fe5992/lib/sinatra/main.rb#L28].

== Command Line

Sinatra applications can be run directly:

  ruby myapp.rb [-h] [-x] [-e ENVIRONMENT] [-p PORT] [-o HOST] [-s HANDLER]

Options are:

  -h # help
  -p # set the port (default is 4567)
  -o # set the host (default is 0.0.0.0)
  -e # set the environment (default is development)
  -s # specify rack server/handler (default is thin)
  -x # turn on the mutex lock (default is off)

== The Bleeding Edge

If you would like to use Sinatra's latest bleeding code, create a local
clone and run your app with the <tt>sinatra/lib</tt> directory on the
<tt>LOAD_PATH</tt>:

  cd myapp
  git clone git://github.com/sinatra/sinatra.git
  ruby -Isinatra/lib myapp.rb

Alternatively, you can add the <tt>sinatra/lib</tt> directory to the
<tt>LOAD_PATH</tt> in your application:

  $LOAD_PATH.unshift File.dirname(__FILE__) + '/sinatra/lib'
  require 'rubygems'
  require 'sinatra'

  get '/about' do
    "I'm running version " + Sinatra::VERSION
  end

To update the Sinatra sources in the future:

  cd myproject/sinatra
  git pull

== Further Reading

* {Project Website}[http://www.sinatrarb.com/] - Additional documentation,
  news, and links to other resources.
* {Contributing}[http://www.sinatrarb.com/contributing] - Find a bug? Need
  help? Have a patch?
* {Issue tracker}[http://github.com/sinatra/sinatra/issues]
* {Twitter}[http://twitter.com/sinatra]
* {Mailing List}[http://groups.google.com/group/sinatrarb/topics]
* {IRC: #sinatra}[irc://chat.freenode.net/#sinatra] on http://freenode.net